US10242746B2

US10242746B2 - Shielded vertically stacked data line architecture for memory

Info

Publication number: US10242746B2
Application number: US15/676,659
Authority: US
Inventors: Koji Sakui
Original assignee: Micron Technology Inc
Current assignee: Micron Technology Inc
Priority date: 2013-06-17
Filing date: 2017-08-14
Publication date: 2019-03-26
Anticipated expiration: 2033-06-17
Also published as: US20160019970A1; US9147493B2; US9734915B2; US10643714B2; US20140369116A1; US20190279722A1; US20180122482A1

Abstract

Apparatuses and methods are disclosed, including an apparatus that includes first and second strings of vertically stacked memory cells, and first and second pluralities of vertically stacked data lines. A data line of the first plurality of data lines is coupled to the first string through a first select device. A data line of the second plurality of data lines is coupled to the second string through a second select device and is adjacent to the data line coupled to the first string. Such an apparatus can he configured to couple the data line coupled to the first string to a shield potential during at least a portion of a memory operation involving a memory cell of the second string.

Description

PRIORITY APPLICATION

This application is a continuation of U.S. application Ser. No. 14/867,948, filed Sep. 28, 2015, now issued as U.S. Pat. No. 9,734,915, which is a continuation of U.S. application Ser. No. 13/919,599, filed Jun. 17, 2013, now issued as U.S. Pat. No. 9,147,493, all of which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present embodiments relate generally to memory and a particular embodiment relates to shielded vertically stacked data line architecture for memory.

BACKGROUND

Flash memory devices have developed into a popular source of non-volatile memory for a wide range of electronic applications. Common uses for flash memory include personal computers, personal digital assistants (PDAs), digital cameras, digital media players, digital recorders, games, appliances, vehicles, wireless devices, cellular telephones, and removable memory modules. Flash memory devices typically use a one-transistor memory cell that allows for high memory densities, high reliability, and low power consumption. Changes in threshold voltage of the cells, through programming of a charge storage structure, such as floating gates, trapping layers or other physical phenomena, determine the data state of each cell.

Electronic devices that use memory are continually being designed faster, smaller and more power efficient. In order to remain competitive, memory device manufacturers also have a continual need to increase memory operation speed and reduce the power consumption of memory devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic diagram of one embodiment of a string of memory cells.

FIG. 2 shows a cross-sectional view of one embodiment of a semiconductor construction of a string of memory cells in accordance with FIG. 1.

FIG. 3 shows across-sectional view of one embodiment of a semiconductor construction of a memory cell of the string shown in FIG. 2.

FIG. 4 shows a schematic diagram of a group of memory cells having a vertically stacked data line architecture.

FIG. 5 shows a schematic diagram of one embodiment of a memory operation using a shielded vertically stacked data line architecture in accordance with FIG. 4.

FIG. 6 shows a schematic diagram of another embodiment of a memory operation using a shielded vertically stacked data line architecture in accordance with FIG. 4.

FIG. 7 shows a schematic diagram of another embodiment of a memory operation using a shielded vertically stacked data line architecture in accordance with FIG. 4.

FIG. 8 illustrates a schematic diagram of one embodiment of a circuit configured to couple alternating data lines to different potentials.

FIG. 9 shows a schematic diagram of one embodiment of the circuit of FIG. 8 in accordance with the timing diagrams of FIGS. 10 and 11.

FIG. 10 shows a timing diagram of one embodiment of a sense operation in accordance with the embodiment of FIG. 9.

FIG. 11 shows a timing diagram of one embodiment of a program operation in accordance with the embodiment of FIG. 9.

FIG. 12 shows a block diagram of a system.

DETAILED DESCRIPTION

For the purposes of this document, an “apparatus” can refer to any of a number of structures, such as circuitry, a device or a system. A transistor is described as being enabled to assume an activated state when it is rendered conductive by a control gate voltage that is separated from its source voltage by at least its threshold voltage. The transistor is described as being disabled to assume an inactive state when the difference between the control gate voltage and the source voltage is less than the threshold voltage, so that the transistor is rendered non-conductive. A “potential” is an electrical voltage. Multiple memory cells can be read at the same time during a page read operation where a “page” includes a fixed amount of data, such as two kilobytes of data, within a memory device.

FIG. 1 is a schematic diagram of a string 100 of vertically stacked memory cells formed above a substrate (not shown). For purposes of illustration only, the string 100 is shown having 16

memory cells

112 formed in 16 memory cell tiers (e.g., layers) above the substrate. Alternate embodiments can include more or less than 16

memory cells

112 and/or more or less memory cell tiers. The string 100 includes a source select device 120 that may be an n-channel transistor coupled between one of the memory cells 112 at one end of the string 100 and a common source 126. The common source 126 may comprise, for example, a slot of commonly doped semiconductor material and/or other conductive material. At the other end of the string 100, a drain select device 130 may be an n-channel transistor coupled between one of the memory cells 112 and a data line (e.g., bit line) 134. The common source 126 can be coupled to a reference voltage V_ss(e.g., ground) or a voltage source (e.g., a charge pump circuit not shown).

Each memory cell 112 may comprise, for example, a floating gate transistor or a charge trap transistor and may be a single level charge storage device or a multilevel charge storage device. The memory cells 112, the source select gate transistor 120, and the drain select gate transistor 130 are controlled by signals on their respective control gates, the signals on the control gates of the memory cells 112 being provided access lines (e.g., word lines) WL0-WL15. In one embodiment, the control gates of memory cells in a row of memory cells can at least partially form an access lines.

The source select gate transistor 120 receives a control signal that controls the source select gate transistor 120 to substantially control conduction between the string 100 and the common source 126. The drain select gate transistor 130 receives a control signal that controls the drain select gate transistor 130, so that the drain select gate transistor 130 can be used to select or deselect the string 100. The string 100 can be one of multiple strings of memory cells in a block of memory cells in a memory device, such as a NAND memory device.

FIG. 2 is a cross-sectional view of a semiconductor construction of the string 200 of FIG. 1. The memory cells 112, source select gate transistor 120 and the drain select gate transistor 130 at least partially surround (e.g., surround or partially surround) a semiconductor material 210. The semiconductor material 210, in one embodiment, can comprise a pillar of p-type polysilicon and can be used as a channel for the memory cells 112, the source select gate transistor 120 and the drain select gate transistor 130. The memory cells 112, the source select gate transistor 120 and the drain select gate transistor 130 can thus be associated with the pillar of semiconductor material 210. The pillar of semiconductor material 210 can extend between a source cap 220 (e.g., type polysilicon) and a drain cap 230 (e.g., n+ type polysilicon). The source cap 220 can be in electrical contact with the pillar of semiconductor material 210 and can form a p-n junction with the semiconductor material 210. The drain cap 230 can he in electrical contact with the pillar of semiconductor material 210 and cart form a p-n junction with the semiconductor material 210. The source cap 220 can be a source for the pillar of semiconductor material 210 and the drain cap 230 can be a drain for the pillar of semiconductor material 210. The source cap 220 can he coupled to the common source 126. The drain cap 230 can be coupled to the data line 134.

FIG. 3 is a cross-sectional view of a semiconductor construction of a memory cell 112 of the string 100 associated with the pillar 250 of FIG. 2. The memory cell 112 surrounds or partially surrounds the pillar of semiconductor material 210. The semiconductor material 210, in one embodiment, can comprise p-type polysilicon. The semiconductor material 210 may be surrounded or partially surrounded by a first dielectric 310 (e.g., silicon dioxide (SiO₂)). The first dielectric 310 may be surrounded or partially surrounded by a floating gate material 320 (e.g., polysilicon). The floating gate material 320 may be surrounded or partially surrounded by a second dielectric 330 (e.g., oxide-nitride-oxide or “ONO”). The third dielectric 340 may be surrounded or partially surrounded by a control gate 350 (e.g., polysilicon). The control gate 350 may be surrounded or partially surrounded by a metal material 360.

FIG. 4 is a schematic diagram of one embodiment of a group 400 (e.g., block) of memory cells having a vertically stacked data line architecture. The embodiment illustrated in FIG. 4 illustrates a four layered data line architecture wherein the data lines extend horizontally substantially parallel with the plane of the substrate and each layer is formed vertically above an adjacent layer. The four layers are only for purposes of illustration. Other embodiments can have more or less than four data line layers, such as the two layered architecture that is described subsequently.

The illustrated group (e.g., a block or sub-block) of memory cells 400 includes twelve

strings

402, 404, 406, 408, 412, 414, 416, 418, 422, 424, 426, 428 of memory cells 432. For purposes of illustration, each

string

402, 404, 406, 408, 412, 414, 416, 418, 422, 424, 426, 428 is shown with four memory cells 432, a drain select gate transistor 469-480, and a source select gate transistor 449-460, respectively. Alternate embodiments can include strings with more or less than four memory cells 432.

The source select gate transistor 449-460 for each string can be coupled between one of the memory cells 432 at one end of the string and a single common source 436 for the block 400. In one or more embodiments, the control gates of the source select gate transistors (e.g.,

transistors

449, 450, 451, 452) of a sub-group of strings (e.g., sub-group 441) can be commonly coupled such that the source select gate transistors of that sub-group are commonly controlled. In certain embodiments, the control gates of the source select gate transistors of the entire group 400 can be commonly coupled such that the source select gate transistors of the group are commonly controlled. Meanwhile, the drain select gate transistor 469-480 for each string can be coupled at the other end of the string between one of the memory cells 432 and a data line as described below. In one or more embodiments, the control gates of respective drain select gate transistors (e.g.,

transistors

469, 473 and 477) from each sub-group of strings (e.g.,

sub-groups

441, 461 and 481) can be commonly coupled such that a respective drain select gate transistor (e.g., transistor 469) from each sub-group of the group 400 is commonly controlled with respective drain select gate transistors (e.g., transistors 473 and 477) from the other sub-groups of the group 400.

The composition of each of the subsequently described strings of

memory cells

402, 404, 406, 408, 412, 414, 416, 418, 422, 424, 426, 428 can be substantially similar to the string of memory cells 402 previously described. Also, as shown in FIG. 4, control gates of the first memory cell 432 in each of one or more of

strings

402, 404, 406, 408, 412, 414, 416, 418, 422, 424, 426, 428 may be commonly coupled and formed in a first tier above a substrate (not shown). Such an arrangement could be continued throughout the group 400, such as where control gates of second memory cells 432 in each of the one or more of

strings

402, 404, 406, 408, 412, 414, 416, 418, 422, 424, 426, 428 may be commonly coupled and formed in a second tier above the substrate (not shown), control gates of third memory cells in each of the one or more of

strings

402, 404, 406, 408, 412, 414, 416, 418, 422, 424, 426, 428 may be commonly coupled and formed in a third tier above the substrate (not shown), and so forth. As subsequently described, the particular data line to which each string of memory cells shown in group 400 is connected is different.

The strings of

memory cells

402, 404, 406, 408 comprise a first sub-group 441 of strings in the group 400 wherein the control gate of each memory cell 432 of each

string

402, 404, 406, 408 is coupled through a respective access line (e.g., row) to a respective one of the memory cells 432 in the

other strings

402, 404, 406, 408 of the first sub-group 441. The strings of

memory cells

402, 404, 406, 408 are coupled to four

separate data lines

442, 444, 446, 448 in a first plurality of vertically stacked data lines that are located over the

strings

402, 404, 406, 408. The drain select gate transistor 469 of the string 402 is coupled to the data line 442. The drain select gate transistor 470 of the string 404 is coupled to the data line 444. The drain select gate transistor 471 of the string 406 is coupled to the data line 446. The drain select gate transistor 472 of the string 408 is coupled to the data line 448.

The strings of

memory cells

412, 414, 416, 418 comprise a second sub-group 461 of strings in the group 400 wherein the control gate of each memory cell 432 of each

string

412, 414, 416, 418 is coupled through a respective access line (e.g., row) to a respective one of the memory cells 432 in the

other strings

412, 414, 416, 418 of the second sub-group 461. The strings of

memory cells

412, 414, 416, 418 are coupled to tour

separate data lines

462, 464, 466, 468 in a second plurality of vertically stacked data lines. The second plurality of vertically stacked data lines are located over the

strings

412, 414, 416, 418 and are adjacent to the first plurality of data lines (e.g.,

data lines

442, 444, 446, 448) in a direction orthogonal to a direction in which the first plurality of stacked data lines extend. The drain select gate transistor 473 of the string 412 is coupled to the data line 462 and, in one or more embodiments, has a control gate that is commonly coupled with the control gate of drain select gate transistor 469. The drain select gate transistor 474 of the string 414 is coupled to the data line 464 and, in one or more embodiments, has a control gate that is commonly coupled with the control gate of drain select gate transistor 470. The drain select gate transistor 475 of the string 416 is coupled to the data line 466 and, in one or more embodiments, has a control gate that is commonly coupled with the control gate of drain select gate transistor 471. The drain select gate transistor 476 of the string 418 is coupled to the data line 468 and, in one or more embodiments, has a control gate that is commonly coupled with the control gate of drain select gate transistor 472.

The strings of

memory cells

422, 424, 426, 428 comprise a third sub-group 481 of strings in the group 400 wherein the control gate of each memory cell 432 of each

string

422, 424, 426, 428 is coupled through a respective access line (e.g., row) to a respective one of the memory cells 432 in the

other strings

422, 424, 426, 428 of the third sub-group 481. The strings of

memory cells

422, 424, 426, 428 are coupled to four

separate data lines

482, 484, 486, 488 in a third plurality of vertically stacked data lines. The third plurality of vertically stacked data lines are adjacent to the second plurality of data lines (e.g.,

data lines

462, 464, 466, 468) in a direction orthogonal to a direction in which the second plurality of stacked data lines extend. The drain select gate transistor 477 of the string 422 is coupled to the data line 482 and, in one or more embodiments, has a control gate that is commonly coupled with the control gates of drain

select gate transistors

469 and 473. The drain select gate transistor 478 of the string 424 is coupled to the data line 484 and, in one or more embodiments, has a control gate that is commonly coupled with the control gates of drain

select gate transistors

470 and 474. The drain select gate transistor 479 of the string 426 is coupled to the data line 486 and, in one or more embodiments, has a control gate that is commonly coupled with the control gates of drain

select gate transistors

471 and 475. The drain select gate transistor 480 of the string 428 is coupled to the data line 488 and, in one or more embodiments, has a control gate that is commonly coupled with the control gates of drain

select gate transistors

472 and 476.

Adjacent strings

402, 404, 406, 408, 412, 414, 416, 418, 422, 424, 426, 428 in the illustrated group 400 are coupled to

different data lines

442, 444, 446, 448, 462, 464, 466, 468, 482, 484, 486, 488. For example, the

strings

402 and 404 are adjacent in a direction in which the first plurality of data lines extend and are coupled to

different data lines

442 and 444 in the first plurality of vertically stacked data lines. Meanwhile, the strings 402and 412 are adjacent in a direction orthogonal to a direction in which the first plurality of data lines extend and are coupled to

different data lines

442 and 462.

The data lines 442, 462, 482 can be formed from a first layer of conductive material formed in a first tier above the

strings

402, 404, 406, 408, 412, 414, 416, 418, 422 424, 426, 428. The data lines 444, 464, 484 can be formed front a second layer of conductive material formed in a second tier above the

data lines

442, 462, 482. The data lines 446, 466, 486 cart be formed from a third layer of conductive material formed in a third tier above the

data lines

444, 464, 484. The data lines 448, 468 488 can be formed from a fourth layer of conductive material formed in a fourth tier above the

data lines

446, 466, 486.

During first memory operation (e.g., sense), data lines are selected in alternate layers (e.g., every other layer). Unselected data lines in alternate layers (e.g., remaining layers not selected) are coupled to a first shield potential (e.g., ground) during at least a portion of the first memory operation. The unselected data lines can act as a shield for the selected data lines during at least a portion of the first memory operation (e.g., sense). Capacitive coupling between adjacent data lines can thus be reduced by the unselected data lines. Reduced coupling between adjacent data lines can result in improved operating speed during memory operations. During at least a portion of a second memory operation (e.g., program), the unselected data lines, in alternate layers, can be coupled to a second shield potential (e.g., an inhibit potential, such as the supply voltage V_CC) to shield the unselected memory cells coupled to the unselected data lines from programming.

FIG. 5 illustrates a schematic diagram of one embodiment of the first memory operation (e.g., sense) using a shielded, vertically stacked data line architecture illustrated in FIG. 4. FIG. 5 incorporates the semiconductor construction illustrated in FIG. 2 with the vertically stacked data line architecture of FIG. 4. Although each of the data lines in a respective stack of data lines are shown in, for example, FIG. 5 as being vertically aligned with each of the other data lines in the respective stack, one or more of the data lines in a given stack of data lines could alternatively be offset from one or more of the other data lines of such a stack in other embodiments.

The first three

strings

402, 412, 422 of FIG. 5 are discussed subsequently as they correspond to the

sub-groups

441, 461, 481, respectively, of FIG. 4. The remaining

strings

500, 501, 502 have a substantially similar construction (e.g., groups) and operate in a substantially similar fashion.

Referring to both FIGS. 4 and 5, the

strings

402, 412, 422 of FIG. 5 represent the

sub-groups

441, 461, 481 of FIG. 4, respectively. The

strings

402, 412, 422 are shown coupled to a source 436. The vertically stacked

data lines

442, 444, 446, 448, 462, 464, 466, 468, 482, 484, 486, 488 are shown formed above the

strings

402, 412, 422. The data lines 442, 444, 446, 448, 462, 464, 466, 468, 482, 484, 486, 488, as illustrated in FIG. 4, extend into the page along the z-axis.

The schematic diagram of FIG. 5 illustrates that, during at least a portion of the first memory operation (e.g., sense), alternating

unselected data lines

442, 446, 464, 468, 482, 486 are coupled to the first shield potential (e.g., ground) in order to provide shielding for the alternating selected

data lines

444, 448, 462, 466, 484, 488. The alternating selected

data lines

444, 448, 462, 466, 484, 488 are used during the memory operation to determine a state of one or more selected memory cells that are coupled to a respective selected data line. For example, in the embodiment shown in FIG. 5, alternating

data lines

442 and 446, in a stack that also includes selected

data lines

444 and 448, are coupled to the first shield potential. In such an embodiment, data line 442 may be coupled to an unselected string 402,

data lines

444 and 448 may be coupled to selected strings (not shown), and data line 446 may be coupled to an unselected string (not shown). As also shown in FIG. 5, alternating data lines in a respective tier, such as the

data lines

442 and 482 in the tier that also includes selected data line 462, are coupled to the first shield potential. In such an embodiment, data line 442 may be coupled to an unselected string 402, data line 462 may be coupled to a selected string 412, and data line 482 may be coupled to an unselected string 422.

FIG. 6 illustrates a schematic diagram of another embodiment of the first memory operation (e.g., sense) using a shielded, vertically stacked data line architecture in accordance with FIG. 4. FIG. 6 incorporates the semiconductor construction illustrated in FIG. 2 with a portion of the vertically stacked data line architecture of FIG. 4. The embodiment of FIG. 6 uses a two layer data line architecture.

The first three

strings

402, 412, 422 of FIG. 6 are discussed subsequently as they correspond to the

sub-groups

441, 461, 481, respectively, of FIG. 4. The remaining

strings

600, 601, 602 have a substantially similar construction and operate in a substantially similar fashion.

Referring to both FIGS. 4 and 6, the

strings

402 and 412 of FIG. 6 represent adjacent strings of the

sub-groups

441 and 461 of FIG. 4, respectively. The

strings

data lines

442, 444, 462, 464, 482, 484 are shown formed above the

strings

402, 412, 422. The vertically stacked

data lines

442, 444, 462, 464, 482, 484, as illustrated in FIG. 4, extend into the page along the z-axis.

The schematic diagram of FIG. 6 illustrates that, during at least a portion of the first memory operation (e.g., sense),

unselected data lines

442, 444, 482, 484 are coupled to the first shield potential (e.g., ground) and selected

data lines

462, 464, 662, 664 are used during the first memory operation to determine a state of one or more selected memory cells that are coupled to a respective selected data line. In the embodiment shown in FIG. 6 alternating stacks of data lines, such as the stack of data lines including

data lines

442 and 444, and the stack of data lines including

data lines

482 and 484, are shown as being coupled to the first shield potential. For example,

data lines

442 and 482 may he coupled to unselected strings 402 and 422 (while data line 462 may be coupled to a selected string 412). Although not explicitly shown in FIG. 6,

data lines

444 and 484 may be coupled to other unselected strings (not shown) and data line 464 may be coupled to another selected string (not shown).

FIG. 7 illustrates a schematic diagram of another embodiment of the first memory operation (e.g., sense) using a shielded, vertically stacked data line architecture in accordance with FIG. 4. FIG. 7 incorporates the semiconductor construction illustrated in FIG. 2 with a portion of the vertically stacked data line architecture of FIG. 4. The embodiment of FIG. 7 uses a two layer data line architecture.

The first three

strings

402, 412 and 422 of FIG. 7 are discussed subsequently as they correspond to the

sub-groups

441, 461,481, respectively, of FIG. 4. The remaining

strings

700, 701, 702 have a substantially similar construction and operate in a substantially similar fashion.

Referring to both FIGS. 4 and 7, the

strings

402 and 412 of FIG. 7 represent two adjacent strings of the

sub-groups

441 and 461 of FIG. 4, respectively. The

strings

402, 412 and 422 are shown coupled to a source 436. The vertically stacked

data lines

442, 444, 462, 464, 482, 484 are shown formed above the

strings

402, 412 and 422. The data lines 442, 444, 462, 464, 482, 484, as illustrated in FIG. 4, extend into the page along the z-axis.

The schematic diagram of FIG. 7 illustrates that, during at least a portion of the first memory operation (e.g., sense), alternating

unselected data lines

442, 464, 482 are coupled to the first shield potential (e.g., ground) in order to provide shielding for the alternating selected

data lines

444, 462, 484. The alternating selected

data lines

444, 462, 484, are used during the memory operation to determine a state of one or more selected memory cells that are coupled to a respective selected data line. In the embodiment shown in FIG. 7, alternating data lines in a respective tier (e.g., the

data lines

442 and 482 in the tier that also includes selected data line 462) are coupled to the first shield potential. For example,

data lines

442 and 482 may be coupled to unselected strings 402 and 422 (while data line 462 may be coupled to a selected string 412). Meanwhile, although not explicitly shown in FIG. 6, data line 464 (e.g., in a second tier) may be coupled to another unselected string (not shown) while data lines 444 and 484 (also in the second tier) may be coupled to other selected strings (not shown).

Coupling alternating data lines to one of the shield potentials (e.g., ground, V_CC) during at least a portion of the first or a second memory operation (e.g., sense, program) can be accomplished using various circuits and methods. FIG. 8 illustrates a schematic diagram of a circuit configured to couple alternating data lines to a different potential (e.g., ground, V_CC), depending on the memory operation (e.g., sense, program).

FIG. 8 illustrates a plurality of memory cell strings 800-815 that can he formed vertically with respect to a substrate, such as where each of the strings may be similar to string 200 of FIG. 2. The memory cell strings 800-815 can be coupled to either an odd

data line BL

_o 820, 822 or an even

data line BL

_e 821, 823. The odd and even data lines 820-823 can be formed adjacent to each other (e.g., either vertically or horizontally) in an alternate fashion, such as the data lines illustrated in FIG. 4.

The memory cell strings 800-815 can be coupled to

page buffers

850, 851 that can be configured to temporarily store data read from one or more selected memory cells from one or more selected data lines 820-823. The data lines 820-823 are coupled to the page buffers 850, 851 through data

line transfer transistors

840, 842, 844, 846. For example, when a data line has been selected for the first memory operation (e.g., sense), the selected data line's

respective transfer transistor

840, 842, 844, 846 can be enabled to allow current on the selected data line 820-823 to flow to the

respective page buffer

850, 851.

The data lines 820-823 can be coupled to a shield voltage line VSH 830 through data

line shield transistors

841, 843, 845, 847. The shield voltage line VSH 830 can be a common node that can be switched to the different potentials used during at least a portion of the various memory operations (e.g., sense, program). For example, as described previously, when a data line is unselected during the first memory operation (e.g., sense), it can be coupled to the shield voltage line 830 that is at a first potential (e.g., ground) in order to provide shielding for the selected data lines. During at least a portion of this operation, the VSH line 830 can be at the first potential (e.g., ground) and the particular data

line shield transistor

841, 843, 845, 847 for the unselected data lines can be enabled. When a data line is selected, the data

line shield transistors

841, 843, 845, 847 isolate the data line from the VSH line 830.

In another example, when a data line is unselected during the second memory operation (e.g., program), it can be coupled to the second potential (e.g., V_CC) in order to provide the inhibiting for the unselected data lines. During at least a portion of this operation, the VSH line 830 can be at the second potential (e.g., V_CC) and the particular data

line shield transistor

841, 843, 845, 847 for the unselected data lines can he enabled.

By particular example, as shown in FIG. 8, a data line 820 coupled to a first memory cell string 800 and a data line 821 coupled to a second memory cell string 804 are coupled to a common page buffer 850 through first and second data

line transfer transistors

840 and 842, respectively. The first and second data

line transfer transistors

840 and 842 are configured to alternately couple the common page buffer 850 to a respective one of the first and

second data lines

820 and 821. The first and

second data lines

820 and 821 are also coupled to the common node 830 through first and second data

line shield transistors

841 and 843, respectively. The first and second data

line shield transistors

841 and 843 are configured to alternately couple the common node 830 to a respective one of the

data lines

820, 821, such as to alternately provide a shield potential to the

data lines

820, 821.

FIG. 9 shows a schematic diagram of one embodiment of the circuit of FIG. 8 in accordance with the timing diagrams of FIGS. 10 (e.g., sense operation timing) and 11 (e.g., program operation timing). For purposes of clarity, the circuit diagram of FIG. 9 shows only one string of memory cells coupled to each data line. The circuit of FIG. 9 also shows the page buffers 850, 851 in greater detail in order to show their different operations during various memory operations (e.g., sense, program) in conjunction with the respective timing diagrams of FIGS. 10 and 11.

Referring to both the circuit of FIG. 9 and the timing diagram of FIG. 10, a sense operation can comprise initially pre-charging the data lines 820-823 by enabling the

pre-charge transistors

910, 911, that are pulled up to a voltage (e.g., V_CC) with the PRE signal. During the time that CLP is at a positive voltage (e.g., V_CC), the

transistors

904, 905 are enabled and the voltage (e.g., V_CC) can then bias the data lines having enabled

transfer transistors

840, 842, 844, 846. In the illustrated embodiment of FIG. 10, the BLT_osignal is at V_SSso that the

odd transfer transistors

840, 844 are disabled and the

odd data lines

820, 822 are unselected. The BLT_esignal is at a positive voltage (e.g., V_CC) during this time so the

even transfer transistors

842, 846 are enabled and the pre-charge voltage can be used to bias the

even data lines

821, 823. Also during this time, the odd data

line shield transistors

841, 845 are enabled by the BLS_Ovoltage (e.g., V_CC) so that the

unselected data lines

820, 822 can be coupled to the VSH line 830 that can be at V_SS. The BLS_evoltage can be at V_SSso that the even data

line shield transistors

843, 847 are disabled and the even data lines are not coupled to the VSH line 830.

For the sense operation to occur,the unselected access lines WL can be biased at a pass voltage V_PASS _{_} _READwhile the selected access line (not shown) can be biased at a read voltage V_READ. While these pass and read voltages bias the access lines, the select gate drain and source transistors for the selected memory cell strings can be enabled by both SGD and SGS being at a positive voltage (e.g., V_CC). When the SEN1 signal is at a positive voltage (e.g., V_CC),

sense transistors

916, 918 are enabled so that the data read from the selected memory cell(s) can be latched into the

latch circuits

929, 930 of the page buffers 850, 851. The data in the

latch circuits

929, 930 can then be output to the I/O lines when the output enable

transistors

950, 951 are enabled.

Referring to the circuit of FIG. 9 and the timing diagram of FIG. 11, a program operation can comprise the programming transistors 901, 902 being enabled by a positive voltage (e.g., V_CC). Enabling the programming transistors 901, 902 enables the page buffer data that are stored in the

latch circuits

929, 930, to be transferred to the data lines 820-823. However, since the

odd transfer transistors

840, 844 can be turned off by BLT_obeing at V_SSand the

even transfer transistors

842, 846 can be turned on by BLT_ebeing at a positive voltage (e.g., V_CC), the page buffer data can be applied only to the

even data lines

821, 823. The

odd data lines

820, 822 can thus be unselected and the

even data lines

821, 823 can be selected.

During this time, the

odd shield transistors

841, 845 can be turned on by a positive BLS_ovoltage (e.g., V_CC) and the

even shield transistors

843, 847 can be turned off (e.g., BLS_eat V_SS). Since the VSH line 830 can be at a positive voltage (e.g., V_CC), this voltage can be allowed to bias the unselected,

odd data lines

820, 822.

The unselected access lines WL can be biased at a pass voltage V_PASS _{_} _PROGRAMwhile the selected access lines can be biased at a program voltage V_PROGRAM. Also during this time, the select gate drain transistors can be turned on by SGD being at a positive voltage (e.g., V_CC) and the select gate source transistors can be turned off by SGS being at V_SS. The source can also be at a positive voltage (e.g., V_CC) during the programming operation.

FIG. 12 is a block diagram of an apparatus in the form of a memory device 1200 according to various embodiments of the invention. The memory device 1200 is coupled to a control bus 1204 to receive multiple control signals over control signal lines 1205. The memory device 1200 is also coupled to an address bus 1206 to receive address signals A0-Ax on address signal lines 1207 and to a data bus 1208 to transmit and receive data signals. Although depicted as being received on separate physical buses, the data signals could also be multiplexed and received on the same physical bus. The memory device 1200 may be coupled to a processor (not shown) in a system.

The memory device 1200 includes one or more arrays 1210 of memory cells that can be arranged in rows and in columns. The memory cells of the array 1210 can be non-volatile memory cells (e.g., charge storage devices, such as floating gate transistors or charge trap transistors) according to various embodiments of the invention. The memory device 1200 can be a NAND memory device. The array 1210 can include multiple banks and blocks of memory cells residing on a single die or on multiple dice as part of the memory device 1200. The memory cells in the array 1210 can be SLC or MLC memory cells, or combinations thereof. The array 1210 includes one or more of the group 400 of memory cells 432 shown in FIG. 4 according to various embodiments of the invention.

An address circuit 1212 can latch the address signals A0-Ax received on the address signal lines 1207. The address signals A0-Ax can be decoded by a row decoder 1216 and a column decoder 1218 to access data stored in the array 1210. The memory device 1200 can read data in the array 1210 by sensing voltage or current changes in memory cells in the array 1210 using page buffers in a sense/cache circuit 1222. The sense/cache circuit 1222 includes a page buffer 1223 coupled to each of the data lines in the block 400 to sense and latch a data state of the

respective data lines

442, 444, 446, 448, 462, 464, 466, 468, 482, 484, 486 and 488 shown in FIG. 4.

A data input and output (I/O) circuit 1226 implements bi-directional data communication over external (e.g., data I/O) nodes 1228 coupled to the data bus 1208. The I/O circuit 1226 includes N driver and receiver circuits 1240 according to various embodiments of the invention. The memory device 1200 includes a control circuit 1242 that is configured to support operations of the memory device 1200, such as writing data to and/or erasing data from the array 1210. The control circuit 1242 can be configured to implement a state machine and be located on a same or different die than that which includes the array 1210 and/or any or all of the other components of the memory device 1200. The control circuit 1242 can comprise hardware, firmware, software, or combinations of any or all of the foregoing. Data can be transferred between the sense/cache circuit 1222 and the I/O circuit 1226 over N signal lines 1246. As used herein, a controller can refer to, for example, one or more of the following components: control circuit 1242, control logic circuit 1268, row decoder 1216, address circuit 1212, column decoder 1218, sense/cache circuit 455, and/or I/O circuit 1226. In different embodiments, a controller (or components thereof) can be located on a same semiconductor die as the array 1210, or on a different semiconductor die than the array 1210. The above-described embodiments, among others, can be implemented using the controller.

Each driver and receiver circuit 1240 includes a driver circuit 1250. Control signals can be provided to the driver circuits 1250 (e.g., through control logic circuit 1268 that is coupled to the control circuit 1242). The control logic circuit 1268 can provide the control signals over

lines

1270 and 1272 to the driver circuits 1250.

Example structures and methods of blocks of vertical strings of memory cells (e.g., with respect to a substrate) have been described as specific embodiments, but it will be evident that various modifications and changes may be made. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.

CONCLUSION

One or more embodiments provide vertically stacked data lines that can be alternately coupled to a shield potential during at least a portion of a first memory operation (e.g., sense) and/or a second memory operation (e.g., program). By switching unselected data lines, in alternate layers, to a node that is at a first potential (e.g., reference potential, ground) the unselected data lines can act as a shield for the selected data lines, in alternate layers, during at least a portion of the first memory operation (e.g., sense). This can reduce capacitive coupling between adjacent data lines. During at least a portion of the second memory operation (e.g., program), the unselected data lines, in alternate layers, can be switched to the node that is at a second potential (e.g., V_CC) to inhibit programming of the unselected memory cells coupled to the unselected data lines.

The Abstract of the Disclosure is provided to comply with 37 C.F.R. § 1.72(b), requiring an abstract that allows the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the claims. In addition, in the foregoing Detailed Description, it may be seen that various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as limiting the claims. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment.

Claims

What is claimed is:

1. A memory array, comprising:

multiple strings of vertically arranged memory cells, each memory cell including a respective charge storage device, each memory cell string extending between a source and a respective bit line of multiple bit lines, wherein each bit line extends in a first direction;

a first group of memory cell strings each selectively coupled to a first bit line through a respective select device in each memory cell string;

a second group of memory cell strings each selectively coupled to a second bit line through a respective select device in each memory cell string, wherein the second bit line is stacked above the first bit line, and wherein the first and second groups of memory cell strings are interleaved with one another in a second direction orthogonal to the first direction in which the first and second bit lines extend;

access lines coupled to respective memory cells in each of the first and second groups of memory cell strings, each access line configured to allow access to a respective memory cell in each of the first and second groups of memory cell strings to perform a memory operation involving such memory cell;

a memory controller configured to couple the first bit line to a shield potential during at least a portion of a memory operation involving a memory cell in a memory cell string coupled to the second bit line.

2. The memory array of claim 1, wherein memory cell strings of the first and second groups of memory cell strings alternate with one another in the second direction.

3. The memory array of claim 1, further comprising:

a third group of memory cell strings each selectively coupled to a third bit line through a respective select device in each memory cell string of the third group, wherein the third bit line is stacked above the second bit line; and

a fourth group of memory cell strings each selectively coupled to a fourth bit line through a respective select device in each memory cell string of the fourth group, wherein the fourth bit line is stacked above the third bit line; and

wherein the memory controller is further configured to couple the first and third bit lines to a shield potential during at least a portion of the memory operation involving a memory cell in a memory cell string coupled to the second bit line.

4. The memory array of claim 3, wherein the memory controller is further configured to apply a read voltage to the second bit line during a first interval in the performing of the memory operation, and to couple the first and third bit lines to a shield potential during at least a portion of the first interval.

5. The memory array of claim 3, wherein the controller is configured to couple the third data line coupled to the third string of memory cells to the shield potential during at least a portion of a second memory operation involving a memory cell of the fourth group of memory cell strings.

6. The memory array of claim 5, wherein the unselected bit lines are coupled to a ground potential.

7. The memory array of claim 3, wherein the second and fourth bit lines are selected during the memory operation, and wherein the first and third bit lines are unselected during the memory operation.

8. The memory array of claim 1, wherein the first bit line and the second bit line are selectively coupled to a common page buffer through first and second bit line transfer devices, respectively.

9. The memory array of claim 1, wherein the memory operation comprises sensing the memory cell of the second string.

10. The memory array of claim 1, wherein the memory operation comprises programming the memory cell of the second string.

11. A method of operating a memory array having multiple strings of memory cells, each string having multiple charge storage devices and extending between a source and a bit line, comprising:

applying a pass voltage to unselected access lines of multiple access lines coupled to respective memory cells in multiple strings of memory cells;

applying an operational voltage to a selected access line of the multiple access lines to enable particular memory cells in multiple strings of memory cells;

coupling a first bit line of multiple bit stacked bit lines to a shield voltage line during at least a portion of a memory operation, wherein a second bit line extends in a tier above the first bit line;

wherein strings of memory cells comprising the enabled memory cells are operably coupled to the second bit line during the memory operation, and wherein strings of memory cells that do not contain the enabled memory cells are operably coupled to the first bit line during at least a portion of the memory operation.

12. The method of claim 11, wherein the operational voltage is a sense voltage.

13. The method of claim 11, wherein the shield voltage line is at ground potential.

14. The method of claim 13, further comprising enabling select gate drain and select gate source transistors that are coupled to strings of memory cells comprising the enabled memory cells.

15. The method of claim 14, further comprising enabling storing data from selected memory cells in page buffers.

16. The method of claim 11, further comprising disabling select gate drain and select gate source transistors that are coupled to strings of memory cells that do not include the enabled memory cells.

17. The method of claim 11, wherein the operational voltage is a program voltage.

18. The method of claim 11, further comprising applying a ground voltage to the shield voltage line when the operational voltage is a sense voltage.

19. The method of claim 11, further comprising applying a positive voltage to the shield voltage line when the operational voltage is a program voltage.

20. A method of operating a memory array having multiple strings of memory cells, wherein each memory cell string includes multiple charge storage devices and extends between a source and a bit line, and wherein each memory cell string is coupled to a different bit line than each adjacent memory cell string, the method comprising:

applying a read voltage to a selected access line of multiple access lines, each access line coupled to a respective memory cell in each string of a first group of strings of memory cells;

applying a read pass voltage to unselected access lines of the multiple access lines;

applying a pre-charge voltage to a first group of bit lines during a memory operation;

applying a shield voltage to a second group of bit lines during at least a portion of the memory operation; and

applying an enable voltage to select gate drain transistors of a second group of memory cell strings comprising the enabled memory cells to couple the second group of memory cell strings to respective bit lines of the second group of bit lines during the memory operation.

21. The method of claim 20, wherein the first group of bit lines are coupled to respective first bit line shield transistors, and wherein the method further comprises applying a disable voltage to control gates of the first data line shield transistors such that the first group of data lines are not operably coupled to the shield voltage line.

22. The method of claim 21, wherein the second group of data lines are coupled to respective second bit line shield transistors, and wherein applying a shield voltage to the second group of bit lines comprises applying an enable voltage to control gates of the second data line shield transistors such that the second group of data lines are coupled to the shield voltage line.

23. The method of claim 21, further comprising applying an enable voltage to sense transistors that are coupled to the first group of data lines.